Method for dicing wafer and process for manufacturing liquid-discharging head using the dicing method

ABSTRACT

A method for dicing a wafer having a first face in which opening are arranged along dicing streets. The method includes a step of affixing a dicing tape to the first face such that the dicing tape lies over the openings and adhesive regions of the dicing tape are exposed in the openings and a step of treating the dicing tape to reduce the adhesive strength of the adhesive regions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to methods for dicing wafers andparticularly relates to methods for dicing wafers having semiconductorelement sections arranged thereon to separate the semiconductor elementsections. The present invention more particularly relates to a methodfor dicing a wafer having openings arranged in a face thereof and adicing tape affixed to the wafer face to manufacture element substratesfor liquid-discharging heads for discharging liquid from orificesarranged on the front faces of the substrates, the liquid being suppliedfrom supply ports placed on the rear faces of the substrates. Thepresent invention also relates to a method for manufacturing aliquid-discharging head using the dicing method.

2. Description of the Related Art

In general, various semiconductor elements are manufactured by thefollowing procedure: a plurality of semiconductor circuit sections aresimultaneously formed on a silicon wafer or other wafer types, thecircuit sections are separated from each other in a dicing step, andthen processed into sealed packages.

With reference to FIG. 26A, in such a dicing step, a wafer 101 having aplurality of element sections 101 a arranged on the front face thereofis mounted on a dicing tape 110 affixed to a dicing frame K such thatthe rear face of the wafer 101 is in contact with the dicing tape 110.The dicing tape 110 includes a backing 111 and an adhesive 112, placedon the backing 111, for retaining the wafer 101.

The dicing tape 110 is a sheet including an adhesive and a backingcoated therewith. The adhesive 112 contains an ultraviolet-curablecompound such that the element sections 101 a separated can be readilypicked up individually by reducing the adhesive strength of the adhesivein a step subsequent to the dicing step.

The resulting dicing frame K is fixed on a chuck table of a dicingmachine and the alignment of the wafer 101 is performed with analignment device. As shown in FIGS. 26A and 26B, the wafer 101 is cutalong dicing streets 101 b arranged on the wafer 101 using a dicingblade B.

The diced wafer 101 is removed from the dicing machine and the rear faceof the wafer 101 is irradiated with ultraviolet light, whereby theadhesive 112 is cured and thereby reduced in adhesive strength. Thisallows the separated element sections 101 a to be readily peeled offfrom the dicing tape 110 and then separately picked up.

Since the element sections 101 a of the wafer 101 are used as elementsubstrates for liquid-discharging heads, nozzle layers 102 havingorifices 105 for discharging liquid are arranged on the front face ofthe wafer 101 and ink supply ports 103 for supplying ink to the orifices105 are each arranged under the corresponding nozzle layers 102. Eachink supply port 103 communicates with the corresponding orifice 105 withchannels 104 placed therebetween, the channels 104 being arranged in thenozzle layers 102 (see Japanese Patent Laid-Open No. 11-179926,corresponding to U.S. Pat. No. 6,305,080).

Japanese Patent Laid-Open No. 62-79649 discloses that in order toenhance the efficiency of a dicing step by preventing problems such asinsulation faults caused by the adhesion of an adhesive of a dicing tapeto a dicing blade from occurring, the adhesive is partly cured alongdicing streets before dicing is conducted.

Japanese Patent Laid-Open No. 11-111162 discloses that when a protectivetape including an adhesive is affixed to the front face of a wafer andthe wafer is then diced, portions of the adhesive that correspond toelectrode sections (emitter regions) arranged on the wafer are cured ina step conducted prior to the step of affixing the protective tape tothe wafer such that the adhesive is prevented from adhering to theelectrode sections. However, this technique has a problem in thatalignment must be performed before the protective tape is affixed to thewafer, increasing the number of manufacturing steps.

With reference to FIG. 27, since the wafer 101 has the element sections101 a having the ink supply ports 103 arranged under the elementsections 101 a, the adhesive 112 of the dicing tape 110 affixed to therear face of the wafer 101 is exposed in the ink supply ports 103.

Therefore, when the wafer 101 is diced with the dicing blade B, theadhesive 112 is partly broken due to micro-vibration indicated by ArrowS during dicing as shown in FIG. 28B to create adhesive particles 112 a,because the adhesive 112 contains the ultraviolet-curable compound andis therefore soft. The adhesive 112 is particularly soft when itcontains an ultraviolet-curable acrylic compound. The adhesive particles112 a adhere to the edges of the ink supply ports 103 that are openingsarranged under the element sections 101 a as shown in FIG. 28B.Furthermore, cooling water W enters the orifices 105 of the nozzlelayers 102 during dicing to make contact with the adhesive 112 partlyexposed in the ink supply ports 103.

As shown in FIG. 29A, the cooling water W in the orifices 105 is thenremoved from the orifices 105 by air blowing. In this operation, asshown in FIG. 29B, pieces 112 a are removed from the adhesive 112 partlyexposed in the ink supply ports 103 because the adhesive 112 receivesshock from air and the cooling water W. Although most of the removedadhesive particles 112 a are discharged out of the nozzle layers 102together with the cooling water W, a small amount of the adhesiveparticles 112 a cannot be removed and therefore remain around theorifices 105.

It is known that a low-molecular weight component is eluted from theadhesive 112 into pure water although the amount of the eluted componentis small. The eluted component as well as the adhesive particles 112 aremains around the orifices 105 in some cases.

After the dicing tape 110 affixed to the rear face of the wafer 101 isirradiated with ultraviolet light and the adhesive strength of theadhesive 112 is thereby reduced, the element sections 101 a separatedfrom each other by dicing are removed from the dicing tape 110 and thenpicked up. The adhesive particles 112 a present around the orifices 105remain as they are after pickup is performed. Furthermore, the adhesiveparticles 112 a probably remain as they are after the element sections101 a used as elements are subjected to a step subsequent to a mountingstep. This causes the following problems: the adhesive particles 112 aremaining in the element sections 101 a cause a failure in dischargingdroplets from liquid-discharging heads and the adhesive particles 112 aare dispersed in ink to block the orifices 105.

SUMMARY OF THE INVENTION

The present invention is directed to a method for dicing a wafer havingopenings arranged in a face thereof and a process for manufacturing aliquid-discharging head using the dicing method. The dicing methodprevents adhesive cutting dust from remaining in the openings when thewafer is diced.

In other words, the dicing method prevents adhesive particles and/or alow-molecular weight component, created from an adhesive included in adicing tape in a step of dicing the wafer, from remaining in elementsarranged on the wafer to prevent problems from occurring and is usefulin manufacturing a liquid-discharging head in which no orifice pluggingnor a failure in discharging occurs and which has high quality andreliability.

In one aspect of the present invention, a method for dicing a waferhaving a first face, dicing streets, and opening arranged along thedicing streets, is provided. This dicing method includes a step ofaffixing a dicing tape having adhesive regions to the first face suchthat the dicing tape lies over the openings and the adhesive regions areexposed in the openings, and a step of treating the dicing tape toreduce an adhesive strength of the adhesive regions.

Further features and advantages of the present invention will becomeapparent from the following description of exemplary embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary sectional view showing a part of a wafer havinga dicing tape affixed thereto.

FIGS. 2A and 2B are illustrations showing a former part of a dicing stepaccording to a first embodiment of the present invention.

FIGS. 3A and 3B are illustrations showing a latter part of the dicingstep according to the first embodiment.

FIG. 4 is an illustration showing chips used for the alignment of thewafer.

FIG. 5 is an illustration showing the wafer and a light-shielding maskaligned therewith; FIGS. 5A to 5C are schematic views showing the sizeof light-transmissive sections arranged in the light-shielding mask;FIG. 5D is a schematic view showing a operation of aligning the waferwith the light-shielding mask; FIG. 5E is a partially enlarged view ofcircle D shown in FIG. 5D.

FIG. 6 is an illustration showing the depth of a portion that a dicingblade penetrates.

FIG. 7 is an illustration showing a principal part of aliquid-discharging head.

FIG. 8 is a perspective view showing the whole of the liquid-discharginghead.

FIGS. 9A and 9B are illustrations showing an increase in pattern sizeoccurring in a partly cured region.

FIG. 10 is an enlarged fragmentary sectional view showing a dicingmethod according to a second embodiment of the present invention.

FIGS. 11A and 11B are illustrations showing a dicing step according tothe second embodiment.

FIG. 12 is an illustration showing the size of a light-shielding maskaccording to the second embodiment.

FIG. 13 is an illustration showing a variation of the method accordingto the second embodiment.

FIGS. 14A and 14B are illustrations showing an increase in pattern sizeoccurring in a region partly cured in a step included in a dicing methodaccording to a third embodiment.

FIG. 15 is an illustration showing the pattern of light-transmissivesections, arranged in a light-shielding mask, corresponding to dicingstreets.

FIG. 16 is an illustration showing the depth of a portion that a dicingblade penetrates.

FIG. 17 is an illustration showing cutting dust created during dicing.

FIGS. 18A and 18B are illustrations showing a dicing method forcomparison, the method being used in a situation in which dicing streetshave a width equal to that of cured regions of an adhesive layer.

FIGS. 19A and 19B are illustrations showing a former part of a dicingstep according to a third embodiment of the present invention.

FIGS. 20A-C are illustrations showing a latter part of the dicing stepaccording to the third embodiment.

FIG. 21 is an illustration showing a variation of the dicing stepaccording to the third embodiment.

FIG. 22 is an illustration showing another variation of the dicing stepaccording to the third embodiment.

FIGS. 23A and 23B are illustrations showing another variation of thedicing step according to the third embodiment.

FIGS. 24A-C are illustrations showing a dicing method according to afourth embodiment of the present invention.

FIGS. 25A-C are illustrations showing light-transmissive sectionsarranged in a light-shielding mask according to the fourth embodiment.

FIGS. 26A and 26B are illustrations showing a known dicing method.

FIG. 27 is a fragmentary sectional view showing a part of a wafer shownin FIG. 26.

FIG. 28 is an illustration showing a former part of a dicing stepincluded in a known dicing method; FIG. 28A is a schematic fragmentarysectional view showing a part of a wafer subjected to dicing, and FIG.28B is a partially enlarged view of circle A shown in FIG. 28A.

FIG. 29 is an illustration showing a latter part of the dicing step ofthe known dicing method; FIG. 29A is a schematic fragmentary sectionalview showing a part of the wafer subjected to cleaning conductedsubsequent to dicing, FIG. 29B is a partially enlarged view of circle Bshown in FIG. 29A, and FIG. 29C is a partially enlarged view of circle Cshown in FIG. 29A.

DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention will now be described withreference to the accompanying drawings.

First Embodiment

A first embodiment of the present invention provides a dicing methoddescribed below. With reference to FIG. 1, a wafer 1 to be diced haselement sections 1 a, which each include corresponding semiconductorcircuit regions, nozzle layers 2 having orifices 5 and channels 4, andink supply ports (liquid supply ports) 3. The semiconductor circuitregions and the nozzle layers 2 are arranged on the front face of thewafer 1 and form discharging devices. The liquid supply ports 3 extendfrom the rear face of the wafer 1 and communicate with the orifices 5via the channels 4 placed therebetween. These components form elementsubstrates for liquid-discharging heads. A dicing tape 10 including abucking 11 and an adhesive 12 placed thereon is affixed to the rear faceof the wafer 1. The element sections 1 a are separated from each otherby dicing the wafer 1 along dicing streets 1 b extending along cuttinglines. As shown in FIG. 2, before dicing is performed, ultraviolet lightP is applied to the rear face of the wafer 1 using a light-shieldingmask M having perforations (light-transmissive sections) Mo throughwhich light passes and which correspond to the liquid supply ports 3,whereby only regions of the adhesive 12 that correspond to theperforations Mo are reduced in adhesive strength. This leads to theformation of adhesive layers 12 a having low adhesive strength.Therefore, as shown in FIGS. 3A-B, adhesive particles can be preventedfrom being created in the liquid supply ports 3 when the adhesive 12receives shock due to air blowing and/or cooling water W. Even if suchadhesive particles and/or low-molecular weight components are created,they have low adhesive strength and therefore hardly adhere to regionsincluding the orifices 5. Hence, the adhesive particles and/or thelow-molecular weight components hardly remain on the element substratesseparated by dicing as compared to those prepared by the known method.Thus, the following head can be manufactured: a liquid-discharging headin which no orifice plugging nor a failure in discharging due toadhesive particles occurs and which has high quality and reliability.

The wafer 1 is fixed to the dicing tape 10 as shown in FIG. 1, theadhesive 12 is partly irradiated with ultraviolet light using thelight-shielding mask M as shown in FIG. 2A, and the wafer 1 is then cutalong the dicing streets 1 b with the dicing blade B as shown in FIG.2B. The resulting wafer 1 is dried by air blowing as shown in FIG. 3Aand the element sections 1 a are removed from the dicing tape 10 andthen picked up.

In the dicing tape 10, the bucking 11 is a kind of film and the adhesive12 contains a radically polymerizable acrylic compound that isphotocurable and particularly ultraviolet-curable. The dicing tape 10 isbonded to the wafer 1 by the adhesion of the adhesive 12.

The wafer 1 has a thickness of about 600 μm, the adhesive 12 has athickness of about 10 μm, and the bucking 11 has a thickness of 80 μm.

In a step of aligning the light-shielding mask M with the dicing streets1 b extending along the cutting lines, at least two of the elementsections 1 a are used as alignment chips 1 c, of which the liquid supplyports 3 are referred to as apertures 3 a.

FIG. 4 shows the positions of the alignment chips 1 c used in thisembodiment. One of the apertures 3 a is aligned with an alignment holeM3 placed in the light-shielding mask M (shown in FIG. 2A), whereby theposition of the light-shielding mask M is fixed.

In this embodiment, four of the element sections 1 a are used as thealignment chips 1 c. The number of the alignment chips 1 c is notlimited to four. At least two of the alignment chips 1 c may be arrangedclose to the edge of the wafer 1.

In consideration of the width of the dicing streets 1 b and the accuracyin forming the apertures 3 a, the length and width of the apertures 3 aand the those of the alignment hole M3 are set so as to satisfy thefollowing equations:X2=X1+0.1Y2=Y1+0.1wherein X1 represents the width of the apertures 3 a, Y1 represents thelength of the apertures 3 a, X2 represents the width of the alignmenthole M3, and Y2 represents the length of the alignment hole M3 as shownin FIGS. 5A to 5C, those sizes being expressed in μm.

In order to perform alignment, the wafer 1 is turned upside down and thelight-shielding mask M is precisely moved above the wafer 1 in one ofthe directions indicated by the arrows shown in FIGS. 5D and 5E suchthat the alignment hole M3 is aligned with one of the apertures 3 ausing the alignment chips 1 c as standard points. When each alignmentchip 1 c has the three apertures 3 a as shown in FIG. 5A, themisalignment of the apertures 3 a placed on both sides of the center onecan be prevented by aligning the center opening 3 a with the alignmenthole M3.

Since the alignment of the light-shielding mask M is performed using theapertures 3 a arranged in the rear face of the wafer 1 as describedabove, the misalignment between the dicing streets 1 b and regionsirradiated with ultraviolet light P can be controlled within the rangeof about ±30 μm.

In the step of applying ultraviolet light P to the rear face of thewafer 1 using the light-shielding mask M to partly reduce the adhesivestrength of the adhesive 12 to form the adhesive layers 12 a, in orderto prevent radical species from being deactivated due to oxygen in air,it is necessary to reduce the content of oxygen in the atmosphere of theliquid supply ports 3, in which the adhesive 12 is partly exposed, bynitrogen purge or the like. The wafer 1 is housed in a chamber C asshown in FIG. 2A and the oxygen in the atmosphere of the chamber C isreduced to lower than 2% by introducing nitrogen gas into the chamber C.Oxygen in the liquid supply ports 3 is replaced with nitrogen thatenters the liquid supply ports 3 through the orifices 5 and thendiffuses in the liquid supply ports 3 while the chamber C is allowed tostand for a predetermined time. This leads to a decrease in the contentof oxygen in the atmosphere of the liquid supply ports 3 to prevent theradical polymerization activity of the adhesive 12 partly exposed in theliquid supply ports 3 from being reduced.

The intensity of ultraviolet light P used is 600 mJ/cm² (determined at awavelength of 365 nm). The adhesive layers 12 a corresponding to theirradiated regions of the adhesive 12 are semi-cured (or reduced inadhesive strength) or cured (or substantially lost in adhesivestrength). As shown in FIG. 2B, the resulting wafer 1 is diced with thedicing blade B, whereby the element sections 1 a are separated from eachother.

Dicing conditions are as follows: a blade thickness of 50 μm, a feedrate of 30 mm/s, and a blade rotation speed of 50,000 rpm. The elementsections 1 a separated from each other as shown in FIG. 3A are picked upas shown in FIG. 3B.

As shown in FIG. 6, the edge of the dicing blade B penetrates the dicingtape 10 to a depth of about 40 μm and an uncut portion with a thicknessof about 50 μm remains in the dicing tape 10. The dicing blade Bpenetrates the bucking 11 placed under the adhesive 12 to a depth ofabout 30 μm. Since the tip of the edge of the dicing blade B movesacross the wafer 1, the wafer 1 has flat cut faces.

Although micro-vibration occurs at the element sections 1 a duringdicing, the adhesive particles are hardly created in contrast to theknown dicing method because the adhesive 12 has been partly cured asdescribed above. Cooling water W enters the liquid supply ports 3through the orifices 5 extending from the front face of the wafer 1during dicing. Furthermore, cleaning water enters the liquid supplyports 3 in a cleaning step usually performed; hence, the amount of waterin the liquid supply ports 3 is large. Therefore, after dicing isperformed, air is blown onto the nozzle layers 2 having the orifices 5as shown in FIG. 3A, whereby water in the liquid supply ports 3 isremoved.

Although the adhesive layers 12 a exposed in the liquid supply ports 3receives shock due to air and/or water in the liquid supply ports 3, theadhesive layers 12 a are rarely peeled off because they are at leastsemi-cured. Even if the adhesive layers 12 a are peeled off, they hardlyre-adhere to the periphery of the liquid supply ports 3 because theiradhesive strength is slight. Furthermore, since the adhesive layers 12 ahave been subjected to curing, a low-molecular weight component of theadhesive 12 is prevented from being eluted. In the picked-up elementsections 1 a separated by dicing, the adhesive particles and the liketherefore hardly remain in or around the liquid supply ports 3 and theorifices 5.

Although the portions of the adhesive 12 that are exposed in the liquidsupply ports 3 are reduced in adhesive strength as described above,regions of the adhesive 12 that are located directly below the dicingstreets 1 b may be cured (or lost in adhesive strength).

FIGS. 7 and 8 separately show a principal portion of aliquid-discharging recorder including element substrates 13 a and 13 b,prepared by the dicing method of this embodiment, for liquid-dischargingheads. The element substrates 13 a and 13 b obtained by dicing the wafer1 are fixed to a mounting substrate 14 in such a manner that the rearfaces thereof are in contact with the mounting substrate 14. Theresulting element substrates 13 a and 13 b are electrically connected toa flexible wiring member 15, whereby a liquid-discharging head isprepared. Furthermore, an ink supply unit 16 and a tank holder 17 areattached to the liquid-discharging head, whereby a liquid-discharginghead cartridge is prepared. After an ink tank 18 is provided in the tankholder 17, ink can be discharged from the liquid-discharging head.

Since the liquid-discharging recorder includes the liquid-discharginghead including element substrates 13 a and 13 b obtained by the dicingmethod of this embodiment, droplets are not discharged in randomdirections but can be constantly discharged from the liquid-discharginghead. Furthermore, since orifice plugging and a failure in dischargingdo not occur during the use of the liquid-discharging recorder for along time, the liquid-discharging recorder is high in reliability.

Another type of dicing tape including a thermosetting adhesive may beused instead of the dicing tape 10 including the ultraviolet-curableadhesive 12. In this case, regions of the thermosetting adhesive fromthe liquid supply ports 3 can be reduced in adhesive strength byselectively applying heat to the exposed regions; hence, the sameadvantages as those described above can be obtained. However, since heatis used, it is more difficult to define the regions of which theadhesive strength is reduced as compared to the use of theultraviolet-curable adhesive 12. The ultraviolet-curable adhesive 12 isparticularly superior to the thermosetting adhesive in processing thefine element sections 1 a used in this embodiment.

In this embodiment, the element sections 1 a each have one liquid supplyport 3. Each element section 1 a may have a plurality of the liquidsupply ports 3 arranged alternately or in parallel.

Second Embodiment

A second embodiment of the present invention will now be described withreference to FIGS. 9 to 13.

In the first embodiment, the wafer 1 is loosely fixed during dicingafter the adhesive 12 is partly cured prior to dicing. Therefore,minimum regions of the adhesive 12 are selectively cured. However, thewidth of the adhesive layers 12 a that are formed by curing regions ofthe adhesive 12 as described above before dicing is performed increaseswith an increase in the dose (irradiation dose) of ultraviolet light;hence, the cured regions are apt to have a width greater than a requiredvalue. This phenomenon is referred to as an increase in pattern size andcaused by the scattering of a portion of ultraviolet light incident onthe backing 11. In general, in order to prevent an adhesive of a dicingtape from remaining on separated elements during the pick up of theelements, the adhesive has a thickness less than that of a backing.Therefore, ultraviolet light is mostly scattered by the irregularsurface of the baking when it is incident on the backing surface orscattered while it is passing through the backing and the interfacebetween the backing and the adhesive, the interface havingirregularities.

The amount of scattered light increases with an increase in the width ofperforations of a light-shielding mask although the irradiation dose isconstant. This leads to an increase in the magnitude of the increase inpattern size. A part of ultraviolet light applied to the adhesive of thedicing tape is absorbed by the adhesive, which is partly cured. Anotherpart thereof passes through the adhesive to reach liquid supply portsand is then reflected by the walls of the liquid supply ports and theadhesive is further irradiated with the reflected light. This phenomenongreatly depends on the fact that the spaces in the liquid supply portshave a three-dimensional structure in which incident light is reflectedor scattered. This phenomenon is particularly serious when the spaceshave such a reflector shape that the spaces are enlarged from the frontface of the wafer toward the rear face thereof.

With reference to FIG. 9A, the area of the adhesive layers 12 a formedby partly curing the adhesive 12 is greater than that of theperforations Mo of the light-shielding mask M because of the effects ofthe scattered or reflected light described above. This prevents thewafer 1 from being securely fixed on the dicing tape 10 with adhesive 12to cause problems such as chipping (the damage of the wafer 1) duringdicing.

With reference to FIG. 9B, the cured regions extend close to the dicingstreets 1 b. In this case, paths are formed between the dicing streets 1b and the liquid supply ports 3 because of vibration during dicing anddicing particles H enter the liquid supply ports 3 at high speed throughthe paths and adhere to the walls of the orifices 5. This causesfailures. Furthermore, if the cured regions extend over the rear facesof the element sections 1 a, chipping occurs during dicing.

In order to prevent these problems, the area of the cured regions of theadhesive 12 may be controlled by adjusting the irradiation dose ofultraviolet light. However, in consideration of differences in curingproperty between dicing tapes manufactured in different batches, it isnecessary to precisely control the irradiation dose when the adhesive 12is partly cured, because the cured regions are peeled off from the wafer1 after the adhesive 12 is partly cured by the irradiation ofultraviolet light.

A second embodiment of the present invention provides a dicing methoddescribed below. In this embodiment, in order to precisely control curedregions of an adhesive 12 without depending on the irradiation dose, alight-shielding mask N shown in FIGS. 10 and 12 is used. Thelight-shielding mask N includes first mask sections Ne each havingcorresponding perforations (light-transmissive sub-sections) No thoughwhich light passes and which have substantially the same size as that ofthe cured regions of the adhesive 12 and further includes second masksections Nc, each placed at corresponding center portions of theperforations No, for blocking light.

A silicon wafer 1 having a (111) surface is prepared. The (111) surfaceof the wafer 1 is anisotropically etched, whereby liquid supply ports 3are formed. The liquid supply ports 3 are enlarged from the front faceof the wafer 1 toward the rear face thereof. Walls of the liquid supplyports 3 form an angle of about 55 degrees with the rear face of thewafer 1. A dicing tape 10 affixed to the rear face of the wafer 1includes a bucking 11 which is a kind of film and a radicallypolymerizable acrylic adhesive 12 which contains a ultraviolet-curablematerial, which has a predetermined adhesive strength, and which isplaced on the bucking 11. The wafer 1 has a thickness of about 600 μm,the adhesive 12 has a thickness of about 10 μm, and the bucking 11 has athickness of about 80 μm. The adhesive strength of the adhesive 12 usedin this embodiment is decreased to about one fifteenth of its originalstrength by irradiating the adhesive 12 with ultraviolet light. Thelight-shielding mask N is aligned with the wafer 1 by the proceduredescribed above with reference to FIGS. 4 and 5.

In order to prevent radical species from being deactivated due to oxygenin air, it is necessary to reduce the content of oxygen in theatmosphere of the liquid supply ports 3 by purging oxygen molecules fromthe liquid supply ports 3 using nitrogen gas or the like prior to theirradiation of ultraviolet light. Therefore, as shown in FIG. 11A, thewafer 1 is housed in a chamber C and nitrogen gas is introduced into thechamber C, whereby the content of oxygen in the atmosphere of thechamber C is reduced to less than 2%. The resulting chamber C is allowedto stand for a predetermined time. This leads to a decrease in thecontent of oxygen in the atmosphere of the liquid supply ports 3 toprevent the radical polymerization activity of the adhesive 12 partlyexposed in the liquid supply ports 3 from being reduced.

The intensity of ultraviolet light P used is 600 mj/cm² (determined at awavelength of 365 nm). Irradiation conditions of ultraviolet light P maybe selected such that adhesive layers 12 a with low adhesive strengthare formed by irradiating the dicing tape 10, affixed to the rear faceof the wafer 1, with ultraviolet light P and becomes substantiallytack-free.

The regions of the adhesive 12 that have been irradiated withultraviolet light P are converted into adhesive layers 12 a having lowor substantially no adhesive strength. Other regions of the adhesive 12that have not been irradiated with ultraviolet light P retain theiradhesive strength during a dicing step shown in FIG. 11B, and thereforesecurely fix the wafer 1 to the dicing tape 10.

FIG. 12 shows the light-shielding mask N which includes a chromium layerfor blocking ultraviolet light, which functions as a photomask, andwhich is in contact with the rear face of the wafer 1. With reference toFIG. 12, the two element sections 1 a are arranged at a pitch of about2,080 μm. Although one second mask section Nc is omitted from one of theelement sections 1 a that is placed on the left side, this elementsection 1 a has the same configuration as that of one placed on theright side.

The liquid supply ports 3 arranged in the rear face of the wafer 1 havea length of about 6,270 μm and a width of about 1,000 μm. Theperforations No corresponding to the liquid supply ports 3 have a sizegreater than that of the liquid supply ports 3 in view of the accuracyin aligning the wafer 1 with the wafer 1 and have a length of about6,290 μm and a width of about 1,020 μm; that is, each side of theperforations No is about 10 μm longer than that of the liquid supplyports 3. The second mask sections Nc having a length of about 5,470 μmand a width of about 300 μm are each placed in the correspondingperforations No.

FIG. 10 is a sectional view showing the element sections 1 a and thelight-shielding mask N when viewed from the side. The adhesive 12 lyingover the liquid supply ports 3 having a width of about 1,000 μm isdirectly exposed to ultraviolet light P passing through the perforationsNo having spaces with a width of about 360 μm. The irradiated regions ofthe adhesive 12 that are exposed in the liquid supply ports 3 extendfrom the edges of the liquid supply ports 3 to positions about 350 μmapart from the edges. In a sectional view showing the element sections 1a and the light-shielding mask N when viewed in the longitudinaldirection of the perforations No, the relationship between thelight-shielding mask N and the liquid supply ports 3 is the same asdescribed above. A portion of ultraviolet light P passing through theperforations No of the first mask sections Ne is absorbed by theadhesive 12 when first regions of the adhesive layers 12 a are cured,the first regions being each surrounded by first ellipse E. The rest ofultraviolet light P passes through the first regions, is reflected bythe walls of the liquid supply ports 3, and is then applied to secondregions of the adhesive layers 12 a that are covered with the secondmask sections Nc, the second regions being each surrounded by secondellipse F as shown in FIG. 10.

The walls of the liquid supply ports 3 formed by an anisotropic etchingprocess are inclined and are not completely flat but are irregular. Aportion of ultraviolet light P entering the liquid supply ports 3 isscattered by the irregularities of the inclined walls of the liquidsupply ports 3. Therefore, although the perforations No each havecorresponding zones with an area less than that of the liquid supplyports 3 when viewed in the direction of the rear face of the wafer 1,the second regions covered with the second mask sections Nc are cured bythe effect of ultraviolet light P that is scattered by theirregularities of the inclined walls after it passes through the dicingtape 10.

According to experiments conducted by the inventors, the cured regionsof the adhesive 12 have a width of about 1,100 to 1,200 μm, includingsub-regions which are located under center portions of the liquid supplyports 3 and which are covered with the second mask sections Nc.

After the adhesive 12 is partly cured, the wafer 1 is diced with adicing blade B, whereby the element sections 1 a are separated from eachother. Dicing conditions are as follows: a blade thickness of 50 μm, afeed rate of 30 mm/s, and a blade rotation speed of 50,000 rpm. Aprocedure of dicing the wafer 1 with the dicing blade B is the same asthat described in the first embodiment with reference to FIG. 6.

Although micro-vibration occurs in the wafer 1 during dicing, piecesthat may be removed from the adhesive layers 12 a having low adhesivestrength by the micro-vibration cannot adhere to areas around orifices 5connected to the liquid supply ports 3.

In a step of removing cooling water that enters the liquid supply ports3 through the orifices 5 during dicing or during cleaning performedsubsequent to dicing from the liquid supply ports 3 by air blowing,shock is applied to the adhesive layers 12 a exposed in the liquidsupply ports 3 from air and water flowing into the liquid supply ports3. However, since the adhesive layers 12 a have been cured, pieces arehardly removed from the adhesive layers 12 a. Even if such pieces areremoved-therefrom, the pieces cannot adhere to areas around the liquidsupply ports 3.

According to this embodiment, the cured regions of the adhesive 12 thathave low adhesive strength can be precisely defined. This preventsproblems from occurring during dicing performed subsequent to curing.

In contrast, if regions of the adhesive 12 that correspond to the liquidsupply ports 3 are irradiated with ultraviolet light P under the sameconditions as described above except the use of the second mask sectionsNc, these regions are cured and have a large width, that is, a width ofabout 1,600 to 1,700 μm, without depending on the irradiation dose. Thiscauses problems such as chipping to occur during dicing.

As shown in FIG. 13, another type of light-shielding mask N may be usedfor irradiation. This light-shielding mask N has perforations(light-transmissive sections) No of which the mouths with an areaslightly less than that of the mouths of the liquid supply ports 3 butincludes no nozzle layers 2. That is, this light-shielding mask N hasopenings through which light passes and which have an area less thanthat of the mouths of the liquid supply ports 3.

In this embodiment, the element sections 1 a each have one liquid supplyport 3. Each element section 1 a may have a plurality of the liquidsupply ports 3 arranged alternately or in parallel.

As shown in FIGS. 7 and 8, the following recorder can be manufacturedusing element substrates prepared by the dicing method of thisembodiment: a liquid-discharging recorder including a liquid-discharginghead including such element substrates. Since the liquid-dischargingrecorder including the liquid-discharging head, droplets are notdischarged in random directions but can be constantly discharged fromthe liquid-discharging head. Furthermore, since orifice plugging and afailure in discharging do not occur during the use of theliquid-discharging recorder for a long time, the liquid-dischargingrecorder is high in reliability.

Third Embodiment

In the second embodiment, in order to prevent problems due to adhesivepieces derived from the dicing tape 10 from occurring, regions of theadhesive 12 that are exposed in the liquid supply ports 3 are cured andtherefore reduced in adhesive strength before dicing is performed,whereby adhesive particles are created from the regions. Furthermore, itis necessary to prevent chippings from being created from portions ofthe adhesive 12 that correspond to the dicing streets 1 b extendingalong cutting lines along which the wafer 1 is diced. In order toprevent such adhesive chippings from being created from the adhesive 12subjected to dicing using a blade, the portions of the adhesive 12,which is included in the dicing tape 10, are cured before dicing isperformed.

There are problems described below when the following regions andportions are simultaneously cured and therefore reduced in adhesivestrength: the regions of the adhesive 12 that are exposed in the liquidsupply ports 3 and the portions of the adhesive 12 that correspond tothe dicing streets 1 b.

As shown in FIG. 14A, a light-shielding mask M has firstlight-transmissive sections M1 for curing the regions of the adhesive 12that are exposed in the liquid supply ports 3 and secondlight-transmissive sections M2 corresponding to the dicing streets 1 b.The width d1 of the first light-transmissive sections M1 is set to about1,020 μm when the width d3 of the liquid supply ports 3 is, for example,about 1,000 μm; that is, the width d1 of the first light-transmissivesections M1 is close to the width d3 of the liquid supply ports 3. Thewidth d2 of the second light-transmissive sections M2 is set to about120 μm when a dicing blade used has a thickness of about 50 μm; that is,the width d2 of the second light-transmissive sections M2 is between twoto three times the thickness of the dicing blade.

In order to prevent such adhesive chippings from being created, it isnecessary to sufficiently cure zones of the adhesive 12 that the dicingblade penetrates. Therefore, in order to form adhesive layers 12 a bycuring regions of the adhesive 12 that correspond to the liquid supplyports 3 and in order to form adhesive layers 12 b by curing regions ofthe adhesive 12 that correspond to the dicing streets 1 b under the sameirradiation conditions (at the same irradiation dose), exposureconditions for forming the adhesive layers 12 b are primarily selected;hence, the lower limit of the irradiation dose of ultraviolet light P islimited.

With reference to FIG. 14B, although the width of the adhesive layers 12a is determined depending on that of the first light-transmissivesections M1 and the width of the adhesive layers 12 b is determineddepending on that of the second light-transmissive sections M2, thewidth of the adhesive layers 12 a exceeds that of the firstlight-transmissive sections M1 and the width of the adhesive layers 12 bexceeds that of the second light-transmissive sections M2 becauseultraviolet light P is scattered or reflected by the rear face of thewafer 1 when it passes through the bucking 11. This phenomenon isreferred to as an increase in pattern size.

If the irradiation dose of ultraviolet light P is constant, the increasein pattern size increases with the size of the first and second firstlight-transmissive sections M1 and M2. Therefore, the increase in sizeof the adhesive layers 12 a formed by curing regions of the adhesive 12that correspond to the liquid supply ports 3 is more serious than thatof the adhesive layers 12 b formed by curing regions of the adhesive 12that correspond to the dicing streets 1 b. This is because the liquidsupply ports 3 have a three-dimensional structure similar to a reflectorshape and incident light is reflected or scattered in the liquid supplyports 3. If the adhesive layers 12 b are completely cured byirradiation, the resulting adhesive layers 12 b have a width of about150 μm even though the second light-transmissive sections M2 have awidth of about 120 μm, and the adhesive layers 12 a have a width ofabout 1,600 μm even though the first light-transmissive sections M1 havea width of 1,020 μm.

The wafer 1 is loosely fixed during dicing after the adhesive 12 ispartly cured. Therefore, minimum regions of the adhesive 12 areselectively cured. However, the cured regions of the adhesive 12 thatcorrespond to the liquid supply ports 3 are apt to have a width greaterthan a required value as described above; that is, an increase inpattern size occurs.

A third embodiment of the present invention provides a dicing methoddescribed below. According to this method, adhesive pieces areeffectively prevented from being created from an adhesive of a dicingtape during the dicing of a wafer and the wafer can be securely fixedduring the dicing.

As shown in FIG. 1, the following sections are formed on the front faceof a wafer 1 having dicing streets 1 b for dicing: a large number ofelement sections 1 a for manufacturing element substrates forliquid-discharging heads. A dicing tape 10 including a bucking 11 and anadhesive 12 placed thereon is affixed to the rear face of the wafer 1. Alight-shielding mask M having light-transmissive sections M2 throughwhich light passes is aligned with the wafer 1 by the proceduredescribed above with reference to FIGS. 4 and 5.

As shown in FIGS. 15 and 16, adhesive layers 12 b are formed byirradiating regions of the adhesive 12 with ultraviolet light P passingthrough the light-transmissive sections M2 to cure the regions. Thewidth of the light-transmissive sections M2 is represented by D. Inconsideration of the misalignment between the light-shielding mask M andthe dicing streets 1 b, the following inequality is set:E>Cwherein E represents the width of the adhesive layers 12 b and Crepresents the design value of the width of dicing streets 1 b.

In this embodiment, the design value C of the width of dicing streets 1b is about 80 μm and the width D of the light-transmissive sections M2is about 150 μm in consideration of the misalignment between thelight-shielding mask M and the wafer 1.

With reference to FIG. 16, the design value C of the width of dicingstreets 1 b is less than the width E of the adhesive layers 12 b becausethe width E of the adhesive layers 12 b is set in consideration of themisalignment described above. Therefore, a dicing blade B does notpenetrate uncured regions 12 c of the adhesive 12 that have adhesivestrength. Since the dicing tape 10 is securely bonded to the wafer 1having the element sections 1 a, the element sections 1 a are preventedfrom being scattered and the wafer 1 and/or the element sections 1 a areprevented from being chipped during dicing.

As shown in FIG. 17, first cutting dust H1 and second cutting dust H2are created from the wafer 1 and the cured regions of the dicing tape10, respectively, during dicing and then scattered due to the rotationof the dicing blade B. The first cutting dust H1 and the second cuttingdust H2 adhere to the wafer 1 during dicing. The resulting first cuttingdust H1 can be removed from the wafer 1 in a cleaning step conductedsubsequent to dicing. The resulting second cutting dust H2 can also beremoved from the wafer 1 in the cleaning step because it has beencreated from the cured regions of the dicing tape 10 and therefore haslow adhesive strength.

FIG. 18 shows a dicing method for comparison. When the design value C ofthe width of dicing streets 1 b is equal to the width E of the adhesivelayers 12 b, the following problem can occur: a problem in that thedicing blade B penetrates a portion seriously apart from the adhesivelayers 12 b formed by partly curing the adhesive 12. This problem is dueto the misalignment δ1 between the center of the dicing blade B and thatof the dicing streets 1 b and the misalignment δ2 between thelight-shielding mask M and the wafer 1. That is, the dicing blade B maypenetrate the uncured regions 12 c having adhesive strength; hence,adhesive cutting dust is scattered. This problem is the same as thatarising from known dicing methods.

However, in this embodiment, as shown in FIGS. 19A-B, the rear face ofthe wafer 1 is irradiated with ultraviolet light P using thelight-shielding mask M before dicing is conducted and only regions ofthe adhesive 12 that correspond to the liquid supply ports 3 or thedicing streets 1 b are thereby cured and therefore reduced in adhesivestrength. In this operation, the regions of the adhesive 12 thatcorrespond to the liquid supply ports 3 are converted into adhesivelayers 12 a and the regions of the adhesive 12 that correspond to thedicing streets 1 b are converted into the adhesive layers 12 b. Theadhesive layers 12 a and 12 b have low adhesive strength. Therefore, asshown in FIG. 20, when shock is applied to the element sections 1 a byair blowing conducted to remove cooling water W entering the liquidsupply ports 3 during dicing, adhesive particles are prevented frombeing created in the liquid supply ports 3. Even if such adhesiveparticles and/or low-molecular weight components are created, theadhesive particles and/or the low-molecular weight components have lowadhesive strength and cannot therefore adhere to areas around orifices 5arranged in nozzle layers 2 included in the element sections 1 a.Furthermore, adhesive pieces can be prevented from being created fromany portion that the dicing blade B penetrates.

The light-shielding mask M further has first light-transmissive sectionsMa which correspond to the liquid supply ports 3, which is opaque, andwhich has low ultraviolet transmission. The first light-transmissivesections Ma are useful in preventing the increase in pattern size fromoccurring when the adhesive 12 is partly cured; hence, the wafer 1 canbe securely fixed or retained during dicing.

Since dicing can be efficiently performed without causing problemsarising from adhesive pieces, the following head can be manufacturedwithout causing any problems: a liquid-discharging head in which noorifice plugging nor a failure in discharging due to adhesive particlesoccurs and which has high quality and reliability.

The shape of the liquid supply ports 3 and the configuration of adhesionof the dicing tape 10 are the same as described above.

As shown in FIG. 19A, the rear face of the wafer 1 is irradiated withultraviolet light P, obtained from an ultraviolet irradiation systemincluding a high-pressure mercury-vapor lamp, using the light-shieldingmask M. The adhesive 12 is usually cured by irradiating the adhesive 12with ultraviolet light having an intensity of about 400 mJ/cm²(determined at a wavelength of 365 nm). In this embodiment, ultravioletlight P having an intensity of about 600 mJ/cm² (determined at awavelength of 365 nm) is applied to the bucking 11 with the ultravioletirradiation system, whereby the adhesive 12 is partly cured and thecured parts become tack-free. In this operation, as described above withreference to FIG. 2, in order to prevent radical species from beingdeactivated due to oxygen in air, it is necessary to reduce the contentof oxygen in the atmosphere of the liquid supply ports 3, in which theadhesive 12 is partly exposed, by introducing nitrogen gas into theliquid supply ports 3. This leads to a decrease in the content of oxygenin the atmosphere of the liquid supply ports 3 to prevent the radicalpolymerization activity of the adhesive 12 partly exposed in the liquidsupply ports 3 from being reduced.

With reference to FIG. 19B, the light-shielding mask M used forultraviolet irradiation, which is a kind of photomask including achromium layer for blocking ultraviolet light, further includes secondlight-transmissive sections Mb corresponding to the dicing streets 1 b.The light-shielding mask M is applied to the bucking 11 of the dicingtape 10 affixed to the rear face of the wafer 1 in such a manner thatthe first and second light-transmissive sections Ma and Mb correspond tothe element sections 1 a arranged on the front face of the wafer 1 atintervals of about 2,080 μm. The element sections 1 a may be referred toas chips.

Since the dicing blade B used in a subsequent dicing step has athickness of about 50 μm, the width of the second light-transmissivesections Mb is set to about 120 μm in consideration of displacement thatmay occur during dicing.

The mouths of the liquid supply ports 3 have a length of about 6,270 μmand a width of about 1,000 μm. The first light-transmissive sections Mafor subjecting regions of adhesive 12 that lie over the liquid supplyports 3 to exposure have a length of about 6,290 μm and a width of about1,020 μm; that is, the length and width of the first light-transmissivesections Ma are about 10 μm longer than those of the mouths of theliquid supply ports 3. The first light-transmissive sections Ma are nottransparent but opaque as described above. The first light-transmissivesections Ma have an ultraviolet transmittance equal to about 35% of thatof the second light-transmissive sections Mb; that is, the intensity ofultraviolet light passing the first light-transmissive sections Ma isreduced to about one third of its original intensity.

After nitrogen gas is introduced into a chamber C in which the wafer 1is placed and the content of oxygen in the atmosphere of the liquidsupply ports 3 is reduced, ultraviolet light P is applied to the bucking11. The irradiation dose of ultraviolet light P is about 1,200 mJ/cm².Regions of the adhesive 12 that extend along the dicing streets 1 b areirradiated with ultraviolet light P with a dose of about 1,200 mJ/cm²that is about three times greater than the dose that is necessary torender the adhesive 12 tack-free, whereby these regions are cured andconverted into the adhesive layers 12 b. On the other hand, otherregions of the adhesive 12 that lie over the liquid supply ports 3 areirradiated with ultraviolet light P with a dose of about 420 mJ/cm²because the intensity of ultraviolet light P is reduced when ultravioletlight P passes through the first light-transmissive sections Ma, wherebysurface portions of these regions are cured and converted into theadhesive layers 12 a which are tack-free, that is, which are lost inadhesive strength.

The adhesive layers 12 b have a width of about 150 μm, even though thesecond light-transmissive sections Mb have a width of about 120 μm. Theadhesive layers 12 a have a width of about 1,100 μm and a length ofabout 6,350 μm, even though the first light-transmissive sections Mahave a width of about 1,020 μm and a length of about 6,290 μm. When aphotomask having the same configuration as that of the light-shieldingmask M except that first light-transmissive sections Ma have atransmittance of 100% is used for comparison, the adhesive layers 12 ahave a width of about 1,600 μm and a length of about 6,700 μm and thedicing tape 10 has reduced adhesive strength insufficient to securelyfix the wafer 1 during dicing. As is clear from this fact, according tothis embodiment, the surface portions of the adhesive regions lying overthe liquid supply ports 3 can be cured, the increase in pattern size canbe prevented from occurring, and the cured surface portions can becontrolled such that they correspond to the liquid supply ports 3 orslightly extend out of the liquid supply ports 3; hence, problems can beprevented from occurring during dicing.

If the first light-transmissive sections Ma of the light-shielding maskM have an appropriate transmittance and the irradiation dose ofultraviolet light is proper, the following advantages can be achieved:the adhesive regions corresponding to the dicing streets 1 b can besufficiently cured such that dust arising from the adhesive layers 12 bduring dicing have sufficiently low adhesive strength, only the surfaceportions of the adhesive regions lying over the liquid supply ports 3can be cured such that peelings and/or elutants are prevented fromarising from the adhesive layers 12 a, and the increase in pattern sizecan be prevented from occurring in the adhesive layers 12 a such thatchipping is prevented from occurring during dicing.

As shown in FIG. 20A, after the adhesive 12 is selectively cured, thewafer 1 is diced with the dicing blade B, whereby the element sections 1a are separated from each other. The positions of the edge of the dicingblade B, the wafer 1, and the dicing tape 10 during dicing are the sameas those described above with reference to FIG. 6.

FIGS. 20B and 20C each show a step of removing cooling water W, enteringthe liquid supply ports 3 through the orifices 5 (openings through whichliquid such as ink is discharged) during dicing or during cleaningconducted subsequent to dicing, from the liquid supply ports 3 by airblowing, the orifices 5 being arranged in the nozzle layers 2. In thisstep, although shock is applied to the adhesive layers 12 a exposed inthe liquid supply ports 3 from air and water introduced into the liquidsupply ports 3, pieces are hardly removed from the cured surfaceportions of the adhesive layers 12 a. Even if such pieces are removedtherefrom, the pieces cannot adhere to the walls of the liquid supplyports 3 nor areas around the liquid supply ports 3. Thus, as shown inFIG. 20C, no adhesive particles remain in the liquid supply ports 3 whenthe element sections 1 a are picked up.

In this embodiment, the element sections 1 a each have one liquid supplyport 3. Each element section 1 a may have a plurality of the liquidsupply ports 3 arranged alternately or in parallel.

FIG. 21 shows another type of light-shielding mask Me attached toelement sections 1 a each having three liquid supply ports 3. Thislight-shielding mask Me has three first light-transmissive sections Mawith a transmittance of 30% and two second light-transmissive sectionsMc, each placed in the outermost light-transmissive sections Ma, havingtransmittance of 50%. The first light-transmissive sections Macorrespond to the liquid supply ports 3. Therefore, ultraviolet lightcan be applied to adhesive layers 12 a lying over the liquid supplyports 3 with a sufficient irradiation dose and the increase in patternsize can be securely prevented from occurring in adhesive layers 12 blying over dicing streets 1 b surrounding the liquid supply ports 3.

FIG. 22 shows another type of light-shielding mask N including firstlight-transmissive sections Na having a transmittance of 100%, secondlight-transmissive sections Nb having a transmittance of 100%, andlight-blocking sections Nc each placed in the corresponding firstlight-transmissive sections Na. The first light-transmissive sections Nacorrespond to adhesive layers 12 a lying over liquid supply ports 3having a length of about 6,270 μm and a width of about 1,000 μm and havespaces having an area less than that of the mouths of the liquid supplyports 3. The second light-transmissive sections Nb correspond to dicingstreets 1 b. The light-blocking sections Nc has a width of about 300 μmand an area equal to about 38% of that of the mouths of the liquidsupply ports 3. The adhesive layers 12 a and the dicing streets 1 b maybe irradiated with ultraviolet light using the light-shielding mask N.In this operation, the dose of ultraviolet light applied to the adhesivelayers 12 a is less than that applied to the dicing streets 1 b. Thatis, since the light-blocking sections Nc are placed in the firstlight-transmissive sections Na, the dose of ultraviolet light applied tothe adhesive layers 12 a is 38% less than that applied to the firstlight-transmissive sections Na. Ultraviolet light passes through thespaces surrounding the light-blocking sections Nc to cure surfaceportions of the adhesive layers 12 a having a width of about 150 μm andalso passes through the second light-transmissive sections Nb to curethe surface portions; hence, the surface portions over which thelight-blocking sections Nc lie are also cured.

FIGS. 23A-B show a first step of curing adhesive layers 12 a, arrangedin an adhesive 12, lying over liquid supply ports 3 using a firstlight-shielding mask N having no sections similar to the secondlight-transmissive sections Nb described above and also shows a secondstep of curing adhesive layers 12 b arranged in the adhesive 12,extending along dicing streets 1 b using a second light-shielding mask Mhaving no sections similar to the first light-transmissive sections Madescribed above. These steps may be separately performed.

According to this embodiment, when the adhesive 12 of the dicing tape10, which lie over the liquid supply ports 3 arranged in the rear faceof the wafer 1, is partly cured, the dose of ultraviolet light appliedto regions of the adhesive 12 that correspond to the liquid supply ports3 can be controlled to be less than that applied to other regions of theadhesive 12 that correspond to cutting lines; hence, adhesive particlescan be prevented from remaining around the orifices 5 and variousproblems due to shock and vibration occurring during dicing can beeffectively prevented. Accordingly, the following substrates can bemanufactured by the dicing method of this embodiment without causing anyproblems: element substrates for semiconductor devices orliquid-discharging heads with high performance and reliability.

As shown in FIGS. 7 and 8, the following recorder can be manufacturedusing such element substrates prepared by the dicing method of thisembodiment: a liquid-discharging recorder including a liquid-discharginghead including the element substrates. The liquid-discharging head doesnot discharge any droplets in random directions but can constantlydischarge droplets. Furthermore, an adhesive can be prevented fromremaining in chambers in which ink remains for a long time; hence,orifices can be prevented from being plugged with elutants from theadhesive. Therefore, the liquid-discharging recorder has highreliability.

Fourth Embodiment

In the third embodiment, since ultraviolet light is applied to theadhesive regions corresponding to the dicing streets 1 b and thosecorresponds to the liquid supply ports 3 with different doses eachappropriate to the corresponding regions, adhesive cutting dust can beprevented from being created during dicing. A fourth embodiment of thepresent invention provides a method for curing an adhesive included in adicing tape. This method based on the relationship between irradiatedregions of the adhesive which correspond to dicing streets or liquidsupply ports located close to the dicing streets and directions in whichirradiation light is reflected by inner walls of the liquid supply portsand which depend on the internal shape of the liquid supply ports.

FIG. 24A shows one of liquid supply ports 3 arranged in a wafer. Theliquid supply ports 3 have mouths having a rectangular shape with alarge aspect ratio and have spaces. The spaces have a shape similar to atruncated quadrangular pyramid and each has two small trapezoidal wallsS1 and two large trapezoidal walls S2. With reference to FIG. 24B,ultraviolet light P entering each space is reflected by one of the smalltrapezoidal walls S1 and then travels toward one of adhesive layers 12a, arranged in an adhesive 12 included in a dicing tape 10, lying overthe liquid supply ports 3; hence, no problems occur. However, withreference to 24C, ultraviolet light P reflected by one of the largetrapezoidal walls S2 travels toward a site of the adhesive layer 12 athat is located close to a region of the adhesive 12 and is reflected bythe interface between the adhesive layer 12 a and a bucking 11 includedin the dicing tape 10 and/or reflected by particles contained in thebucking 11, whereby regions of the adhesive 12 that are prevented frombeing irradiated with ultraviolet light P are cured. Therefore, whendicing streets 1 b extending along sides of the large trapezoidal wallsS2 are located close to the liquid supply ports 3, the adhesive layers12 a cured by ultraviolet light P are connected to cured adhesive layers12 b which are arranged in the adhesive 12 and which extend over thedicing streets 1 b. In this case, the wafer that must be fixed to theadhesive 12 cannot be fixed thereto; hence, problems such as chippingoccur when the wafer is diced.

FIG. 25 shows a light-shielding mask M having light-transmissivesections with a small size. If the light-shielding mask M is used andlong sides of the mouths of the liquid supply ports 3, the long sidesbeing located adjacent to the dicing streets 1 b, are caused to retreatfrom their original positions, the adhesive layers 12 a can be preventedfrom being connected to the adhesive layers 12 b in contrast to thesituation described above.

With reference to FIGS. 25A-C, a method for curing regions of adhesive12 that correspond to the following ports will now be described: threeliquid supply ports 3 arranged in parallel in a quadrilateral region ofwhich the four sides extend along corresponding dicing streets 1 b. Iffour or more liquid supply ports 3 are arranged therein, advantagesdescribed below can be obtained.

A light-shielding mask M having light-transmissive sections Mo is used.The light-transmissive sections Mo have a transmittance of 35% andcorrespond to the liquid supply ports 3. With reference to FIG. 25A, themouths of the liquid supply ports 3 have a length of about 9,000 μm anda width of about 1,000 μm. With reference to FIG. 25B, the two outermostlight-transmissive sections Mo have a length of about 9,000 μm and awidth of about 500 μm. The longitudinal center line C0 of the centerliquid supply port 3 is aligned with that of the light-transmissivesection Mo corresponding to the center liquid supply port 3. If four ormore liquid supply ports 3 are used, the longitudinal center lines ofthe inner liquid supply ports 3 placed between the two outmost liquidsupply ports 3 are each aligned with the corresponding longitudinalcenter lines of the light-transmissive sections Mo that correspond tothe inner liquid supply ports 3. The three liquid supply ports 3 aredescribed below. As shown in FIG. 25B, the longitudinal center lines C1of the two outermost liquid supply ports 3 are aligned with those of thelight-transmissive sections Mo corresponding to the outermost liquidsupply ports 3. The center light-transmissive section Mo has a length ofabout 9,000 μm and a width of about 1,000 μm. Since the size andarrangement of the light-transmissive sections Mo are selected dependingon the shape of the spaces in the liquid supply ports 3 as describedabove, ultraviolet light P reflected by the small trapezoidal walls S1and the large trapezoidal walls S2 can be prevented from being appliedto zones outside the adhesive layers 12 a lying over the liquid supplyports 3, the zones being located close to the dicing streets 1 b, theadhesive layers 12 a being irradiated with ultraviolet light P. That is,the increase in pattern size can be suppressed.

FIG. 25C shows another type of light-shielding mask M having threelight-transmissive sections Mo, corresponding to the liquid supply ports3, for preventing the increase in pattern size from occurring. That is,the light-transmissive sections Mo are useful in preventing regions ofthe adhesive 12 that correspond to areas between the liquid supply ports3 from being cured. The center light-transmissive section Mo has alength of about 9,000 μm and a width of about 600 μm; that is, the rightside and left side of the center light-transmissive section Mo are eachlocated 200 nm closer to the longitudinal center of the centerlight-transmissive section Mo than those of former one described above.The outside light-transmissive sections Mo have a length of about 9,000μm and a width of about 300 μm; that is, the width of these centerlight-transmissive sections Mo is about 200 nm smaller than that offormer ones described above. This configuration is effective inpreventing the increase in pattern size from occurring. Therefore, theadhesive layers 12 a corresponding to the liquid supply ports 3 can beprevented from being connected to regions of the adhesive 12 thatcorrespond to zones between the liquid supply ports 3. Furthermore,regions of the adhesive 12 that correspond to zones between the liquidsupply ports 3 and the dicing streets 1 b adjacent to the liquid supplyports 3 can be prevented from being cured; hence, the adhesive layers 12a are prevented from being connected to the adhesive layers 12 b.

According to this embodiment, the adhesive layers 12 a lying over theliquid supply ports 3 can be prevented from being connected to theadhesive layers 12 b lying over the dicing streets 1 b; hence, theadvantages described above can be securely achieved.

For the configurations described in the first to fourth embodiments withreference to the accompanying drawings, if a light-shielding mask neednot be aligned with a wafer with high accuracy, the size oflight-transmissive sections of the light-shielding mask may be increasedto be greater than that of the mouths of liquid supply ports. If theincrease in pattern size must be suppressed, the size oflight-transmissive sections of the light-shielding mask may be decreasedto be less than that of the mouths of liquid supply ports. Accordingly,the desired advantages described above can be achieved by varyingconfigurations depending on actual conditions.

EXAMPLES

Samples 1 to 6 were prepared, wherein Sample 1 is a comparative exampleand Samples 2 to 6 are examples of the present invention. Each sampleincluded a wafer and 204 element sections arranged thereon, the elementsections being processed into element substrates for liquid-dischargingheads. The element sections each had corresponding liquid supply portsand orifices. The sample was diced and then cleaned. The sample wasinvestigated if there were any adhesive particles on the wafer and ifchipping occurred. In particular, the number of the following particleswas counted: adhesive particles which were bonded to the walls of theorifices and regions around the orifices and which had a particle sizeof 1 μm or less. Table 1 shows results of the investigation.

TABLE 1 Percentage of Area Transmittance Transmittance Covered Sam-Irradiation of Mask of Mask with Chip- ples Dose Sections Mb Sections MaParticles ping 1 Not 100% 100% 100 0/204 Irradiated 2  400 mJ/cm² 100%100% 34 0/204 3 1200 mJ/cm² 100% 0% 14 0/204 4 1200 mJ/cm² 100% 100% 79/204 5 1200 mJ/cm² 100% 35% 8 0/204 6 1200 mJ/cm² 100% 0% 13 4/204

In Table 1, the term “transmittance of mask sections Ma” means thetransmittance of first light-transmissive sections Ma through whichultraviolet light passes and which correspond to liquid supply ports.The term “transmittance of mask sections Mb” means the transmittance ofsecond light-transmissive sections Mb through which ultraviolet lightpasses and which correspond to dicing streets extending along cuttinglines. The term “percentage of area covered with particles” means thepercentage of the area of each sample covered with the adhesiveparticles, the percentage being expressed on the basis that thepercentage of the area of Sample 1, having a dicing tape 10 which wasnot subjected to curing, covered with particles is 100. The percentageof the area of each sample covered with the adhesive particles should besmall.

The term “chipping” means the following problem: the dicing tape,affixed to the rear face of the wafer, for retaining the wafer isreduced in adhesive strength, whereby chips obtained by dicing the waferare damaged during dicing. In Table 1, chipping is represented by theratio of damaged chips to total chips. The number of damaged chipsshould be small.

Table 1 shows that the adhesive particles can be greatly reduced innumber by applying ultraviolet light to adhesive layers 12 b correspondsto the dicing streets with a dose of 1,200 mJ/cm² or more, as is clearfrom the data of Samples 3 to 6. The adhesive particles can be reducedin number by curing adhesive layers 12 a lying over the liquid supplyports, as is clear from the data of Samples 4 and 5. For Sample 5,chipping can be prevented from occurring during dicing because the doseof ultraviolet light applied to the adhesive layers 12 a is equal to 35%of that applied the adhesive layers 12 b. This shows that Sample 5,which is the example of the present invention, is superior.

For Sample 4 , the dose of ultraviolet light applied to the adhesivelayers 12 a is equal to that applied the adhesive layers 12 b; hence,the adhesive layers 12 a of Sample 4 are more greatly cured as comparedto those of Sample 5. Therefore, chippings occurred when Sample 4 wassubjected to dicing.

Table 2 shows the relationship between the dose of ultraviolet light andthe tackiness and elastic modulus of an adhesive, the elastic modulusbeing determined by converting obtained measurements into index valuesby normalizing the elastic modulus of a sample not irradiated withultraviolet light to 1.

TABLE 2 Elastic Irradiation Modulus Dose Tackiness (*) Not IrradiatedTacky 1.0  400 mJ/cm² Tack-free 3.6 1200 mJ/cm² Tack-free 4.3 (*) Theelastic modulus was measured with a microhardness meter.

Table 2 shows that a dose of 400 mJ/cm² is sufficient to cause theadhesive to lose its adhesive strength and the sample irradiated withultraviolet light with a dose of 400 mJ/cm² has an elastic modulus lessthan that of the sample irradiated with ultraviolet light with a dose of1,200 mJ/cm². Therefore, the adhesive of the former sample has beenprobably cured insufficiently.

Samples 4 and 5 are not significantly different in particle creationfrom each other. This shows that the adhesive layers 12 a may be curedsuch that they become tack-free.

The increase in pattern size described above probably causes chipping tooccur in samples irradiated with ultraviolet light. This shows that amethod according to an embodiment of the present invention is effectivein preventing adhesive particles from being created.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed embodiments. On the contrary, the invention isintended to cover various modifications and equivalent arrangementsincluded within the spirit and scope of the appended claims. The scopeof the following claims is to be accorded the broadest interpretation soas to encompass all such modifications and equivalent structures andfunctions.

This application claims priority from Japanese Patent Application Nos.2004-132415 filed Apr. 28, 2004; 2004-135193 filed Apr. 30, 2004;2004-353694 filed Dec. 7, 2004; 2004-353693 filed Dec. 7, 2004; and2005-117693 filed Apr. 15, 2005, which are hereby incorporated byreference herein.

1. A method for dicing a wafer having a first face, dicing streets, andopenings defined in the first face, along the dicing streets, the methodcomprising the steps of: affixing a dicing tape having first adhesiveregions and second adhesive regions to the first face such that thedicing tape lies over the openings, the first adhesive regions areexposed in the openings, and the second adhesive regions correspond tothe dicing streets; and after the affixing step, treating the dicingtape to reduce adhesive strengths of the first and second adhesiveregions such that the adhesive strength of the second adhesive regionsis less than the adhesive strength of the first adhesive regions.
 2. Themethod according to claim 1, wherein the dicing tape includes aphotocurable adhesive, the method further comprising: aligning alight-shielding mask having light-transmissive sections relative to thedicing tape and the wafer; and the treating step including irradiatingthe photocurable adhesive with light via the light-transmissive sectionsto partly reduce the adhesive strength of the photocurable adhesive. 3.The method according to claim 2, wherein the second adhesive regionshave a width greater than that of cut zones of the dicing streets. 4.The method according to claim 2, wherein the aligning step includesaligning the light-shielding mask so that long sides of thelight-transmissive sections that extend along the dicing streets arelocated closer to the openings than the dicing streets.
 5. The methodaccording to claim 2, wherein the openings include at least threeopenings arranged in parallel, and wherein the aligning step includesproviding outermost light-transmissive sections having an area less thanthat of the center light-transmissive section or the innerlight-transmissive sections, and aligning the light-transmissivesections to correspond to the openings.